The invention relates to a vehicle heater and, more particularly, to a vehicle heater for a vehicle equipped with a liquid-cooled internal-combustion engine. A heating circulating system has a heater heat exchanger through which a liquid flows. The heat exchanger is arranged in a passenger compartment and is connected by way of a forward flow pipe and a return flow pipe with the cooling circulating system of an internal combustion engine. A latent heat storage device such as a so-called "PCM device" (phase change material which stores heat) can be switched into the heating circuit. The liquid circulation takes place through the heat exchanger and the latent heat storage device by way of a circulating pump which can be driven independently of the engine and by switch-over valves.
From European Patent document EP-B 340 621, an internal-combustion engine is known which has a heating circulating system into which a latent heat storage device can be switched by means of corresponding switching valves. The latent heat storage device is filled with a salt as a storage medium which, in the case of a phase change from solid to liquid, is capable of storing heat for several days so long as the latent heat storage device housing is constructed in a correspondingly insulated manner.
The arrangement known from European Patent document EP-B 0 340 621 has the purpose of heating the passenger compartment independently of the engine; thus, it is virtually a replacement for the known fuel operated auxiliary heater.
In order to be able to store a corresponding amount of heat, which is sufficient to heat a passenger compartment of a motor vehicle also at outside temperatures of -20.degree. C., to such an extent that at least the windshield is free of condensation, a storage volume of over 10 l is required. The latent heat storage device must be constructed to be correspondingly large.
From Automotive Engineering, February 1992, Pages 58-61, it is known to provide a latent heat storage device with a cylindrical housing and to install this latent heat storage device in the engine compartment.
In the case of a crash, this installation site is disadvantageous because in motor vehicles specifically the forward structure is designed to be relatively soft for the purpose of absorbing energy. In addition, because of the large number of installed assemblies, sufficient space is rarely available in the engine compartment.
From German Patent document DE-A 32 04 519, it is known to house a vacuum reservoir in a motor vehicle in the front passenger's foot space, specifically such that it can be used as a foot rest. Nothing is indicated in this reference concerning the fastening and guiding of the pipes. A leaking of the vacuum reservoir, or of the vacuum pipe, in the case of a crash does not present any problems because the medium cannot flow out of the two devices into the foot space which may otherwise result in injuries in the front passenger's foot/leg space.
In addition to a suitable installation site for a latent heat storage device of the above-mentioned type, there is also needed a type of fastening which is favorable in the event of a crash.
According to the invention, these needs are met by a vehicle heater for a vehicle equipped with a liquid-cooled internal-combustion engine. A heating circulating system has a heater heat exchanger through which a liquid flows. The heat exchanger is arranged in a passenger compartment and is connected by way of a forward flow pipe and a return flow pipe with the cooling circulating system of an internal combustion engine. A latent heat storage device can be switched into the heating circuit. The liquid circulation takes place through the heat exchanger and the latent heat storage device by way of a circulating pump which can be driven independently of the engine and by switch-over valves. The latent heat storage device is installed in the passenger compartment in the area of the front passenger's foot space. The latent heat storage device is held in its position by way of a fastening strap. The forward flow pipe and the return flow pipe for the coolant are arranged laterally on the latent heat storage device by way of couplings.
In addition to the fact that the foot space area on the front passenger side in the case of a crash is not subjected to such intensive deformation as the vehicle forward structure, this installation site has the advantage that, independently of the vehicle type, essentially the same installing conditions will always exist so that an extremely small number of different external forms of latent heat storage devices will suffice for a large number of vehicles. As a result, higher piece numbers are achieved so that the piece-number-dependent manufacturing costs can be significantly reduced. Because a tightening strap for fastening the latent heat storage device is provided, in the case of a deformation of the front wall in this area, it is achieved that the latent heat storage device can escape this deformation because it is no longer connected at several points with the front wall or the floor panel. Thus, it is also possible that the forward flow and return flow pipes of the coolant, in the case of a correspondingly led length, can go along in the escaping of the latent heat storage device without tearing. Because of the also suggested lateral mounting of the two pipes, the pipes extending in the vehicle can be connected with the latent heat storage device by way of a pipe coupling which is designed such that, although the pipes are connected in a liquid-tight manner, they can rotate when subjected to forces which may be released in the case of a crash without any opening of the coupling or tearing-off of the pipes in the coupling. This therefore reliably prevents hot coolant from flowing out into the front passenger's foot space in the case of a crash which otherwise would result in a scaling/burning of the front passenger's feet/legs.
A further development according to the invention has the advantage that the latent heat storage device itself can be used directly as a surface for placing the front passenger's feet. Naturally, for reasons of safety, a step protection plate may be provided between the exterior housing of the latent heat storage device and the normally existing carpet floor in the foot space. However, it is also possible to place the carpet floor directly on the exterior side of the latent heat storage device.
An advantageous design layout for the course of the pipes is also provided. It is also advantageous that additional switching elements, which are required for connecting the latent heat storage device to the heating circulating system according to European Patent Document EP-B 0 340 621, can be mounted on the body shell in a preassembled manner.
In the following, the invention will be explained in detail by means of a preferred embodiment.